Discussion
Early postoperative IOP elevation following cataract surgery is a frequent adverse event and represents 88% of early postoperative complications.5 The release of the MHRA statement added yet another cause for early postoperative rise in IOP. Between January 2022 and September 2022 (before the study period in question), 3% of patients implanted with EyeCee One IOL had an IOP of 30 mm Hg or greater on their first postoperative visit. Between October 2022 and January 2023, 6.2% had an IOP of 30 mm Hg or more on their first postoperative visit after being implanted with an EyeCee One IOL,4 more than double the usual rate.
On 13 July 2023, NIDEK released an updated urgent FSN,6 which states that from their internal investigations, they identified a material used in the coating process to be the causal factor. This coating agent is used to aid the smoothness of the IOL injection, but specific lots have been identified which have physically obstructed the drainage pathway of aqueous humour, likely resulting in abnormally elevated IOP.
This study suggests that in the time frame in question, significant IOP elevations are more likely to occur in patients with glaucoma; 19.6% of the glaucoma cohort had an IOP rise greater or equal to 10 mm Hg, compared with 8.9% of patients without glaucoma (OR 2.49 (95% CI 1.45 to 4.20) p=0.0014). Patients with glaucoma receiving cataract surgery are known to experience more severe IOP rises postoperatively. Shingleton et al7 found IOP greater than 30 mm Hg on the first postoperative day in 8.1% of normal eyes and 15.6% of eyes with glaucoma. But the question is, are patients with glaucoma and OHT even more susceptible to or at a greater risk of the EyeCee One IOL postoperative IOP elevations? As we compared eyes implanted with EyeCee One IOLs with non-EyeCee One IOLs during our study period, we saw significantly higher mean IOP readings on the first postoperative visit in eyes implanted with EyeCee One IOLs compared with non-EyeCee One IOLs, in both glaucoma/OHT (EyeCee One mean postoperative IOP 21.4±10.2 mm Hg compared with 17.8±6.78 mm Hg non-EyeCee One, p=0.040) and non-glaucoma groups (EyeCee One mean postoperative IOP 16.6±7.56 mm Hg compared with 14.5±4.07 mm Hg non EyeCee One, p<0.001), even when the average preoperative IOP was comparable. In fact, in the eyes implanted with EyeCee One IOLs, mean IOP increased from preoperative visit to initial postoperative visit (glaucoma/OHT: preoperative visit 18.8±8.82 mm Hg to postoperative visit 21.4±10.2 mm Hg; non-glaucoma: preoperative visit 14.8±3.77 mm Hg to postoperative visit 16.6±7.56 mm Hg); while in the eyes implanted with non-EyeCee One IOLs, mean IOP decreased (glaucoma/OHT: preoperative visit 18.7±6.50 mm Hg to postoperative visit 17.8±6.78 mm Hg; non-glaucoma: preoperative visit 14.9±3.66 mm Hg to postoperative visit 14.5±4.07 mm Hg).
The EyeCee One glaucoma cohort with a significant IOP rise required more aggressive management in all treatment domains: drops, systemic and surgery. Twelve and a half per cent of the whole glaucoma cohort had an increase in the number of topical IOP-lowering agents (mean increase in agents 1.65±1.58) and 3.3% in the non-glaucoma cohort required topical agents (mean increase in agents 0.88±1.34). A total of 6.3% patients required systemic treatment in the glaucoma cohort and 0.8% in the non-glaucoma cohort; while 2.7% of the glaucoma cohort required surgical intervention compared with the non-glaucoma group where 0.2% required surgical intervention. All differences were statistically significant between the glaucoma and non-glaucoma groups, except surgical intervention where numbers of cases were too small (glaucoma, n=3; non-glaucoma, n=1).
Ninety-one per cent of the patients with glaucoma/OHT who had a significant IOP rise had an IOP <24 mm Hg at the time of the last review. Four patients had an IOP documented as >24 mm Hg after 2 months of the recall date. One case with primary open-angle glaucoma failed to respond to medical management. Excision goniotomy (TrabEx+) was performed a month after cataract surgery. IOP control remained poor as surgery was abandoned early due to poor gonioscopic view. Trabeculectomy was performed and bleb needling was required before IOP reduced to normal levels. In the second case, with primary open-angle glaucoma, the IOP improved with continued topical pressure-lowering medication (two agents), but 2 months of topical steroids was required before IOP reduced to under 24 mm Hg. This patient had cataract surgery in the fellow eye with a similar severity of primary open-angle glaucoma with a different lens implanted by the same surgeon. Interestingly, the postoperative IOP remained well controlled in the non-EyeCee One IOL-implanted eye. The remaining two cases had primary angle closure/glaucoma. Phacoemulsification with IOL was performed primarily for IOP control. One case was treated medically but unfortunately, appointments were not attended. Vision deteriorated to hand movements and the patient declined further intervention. The last case was treated medically but remained poorly controlled. Early anterior chamber washout and lens exchange were performed, but better IOP control was required. Eventually, a Baerveldt tube was inserted at 2 months after cataract surgery.
As more frequent cases of high IOP became evident, discussions occurred internally and with other units. It was theorised that an inflammatory reaction at the level of the trabecular meshwork was responsible. At the end of January 2023, our management plan changed, and later supported by the 13 February 2023 Royal College of Ophthalmologists safety report.8 First-line management was hourly steroid drops alongside IOP-lowering agents. If medical treatment failed, early lens exchange (within 2 weeks) or glaucoma drainage surgery was considered. Since we changed to frequent steroid drop management as first-line therapy, no further surgical interventions, at the time of writing, have been performed to manage sustained raised IOPs, but we acknowledge this is an evolving situation.
As a separate analysis, we looked at patients undergoing cataract surgery (with EyeCee One IOL) combined with excisional goniotomy, namely TrabEx+ (MicroSurgical Technology, Redmond, Washington, USA), a device which mechanically removes a proportion of the trabecular meshwork. These patients were not included in the main body of work as combined glaucoma surgery would affect IOP outcomes. Nine patients received this combined surgery within the same time frame. Of these patients, none had a postoperative IOP elevation of greater or equal to 10 mm Hg, 56% (five out of nine) had no increase in number of drop agents required. In fact, four patients decreased the number of agents they used, with three patients stopping all related glaucoma medications post-procedure. The favourable outcome in this small group supports the theory that the IOP-elevating effect from the IOL is derived from disruption at the level of the trabecular meshwork, which has been prevented by its surgical removal.
Limitations
During the capture of patients, 15 were excluded as they did not have postoperative readings at the time of writing this article.
When analysing data, we did not look at either patients with glaucoma or those without glaucoma who had an IOP rise less than 10 mm Hg. One patient in the glaucoma group whose IOP was less than 10 mm Hg did receive topical treatment, but the focus of this article was on the more significant IOP rises so this case was not included in the analysis. Also, we made no distinction between patients who needed one off-treatment compared with prolonged treatment.
We acknowledge there are several causes for IOP elevations in the early period following cataract surgery; steroid-induced IOP elevation has long been recognised as a big contributor with reports of approximately one-third of normal eyes and over 90% of patients with primary open-angle glaucoma responding with greater than 6 mm Hg of IOP elevation after receiving a 4-week course of topical dexamethasone 0.1%.9 Bojikian et al10 compared both glaucomatous and non-glaucomatous eyes undergoing routine phacoemulsification surgery response to postoperative steroid (prednisolone acetate 1% four times a day). They defined a steroid response as IOP >50% above the baseline IOP measurement, occurring at or after the second postoperative week. We altered the analysis of our results to compare our rates; both our glaucoma and non-glaucoma cohorts showed significantly higher proportion of patients with IOP >50% above the baseline compared with the literature. In our glaucoma cohort, 29.5% met this criterion compared with 8.4% in the literature. Also, 16.1% of our non-glaucoma cohort met the criterion compared with 2.1% in the literature, suggesting that these increases in IOP are being contributed to by more than just a steroid response.